Accessing a Control Outside of an Update Panel

I have a button within an update panel.  I have a button outside the update panel.  The button can't be inside the panel because it contains code that doesn't run within an update panel. I am trying to make the button outside of the update panel visible / not visible depending on when a button is clicked within the update panel.  The code for the button within the update panel fires but the button outside of the update panel doesn't become visible.  Is this possible to access a control outside of the update panel programmatically?  Thanks for your help.